Electrosurgical Systems and Printed Circuit Boards for Use Therewith

ABSTRACT

An electrosurgical system for treating tissue is disclosed. The system includes an electrosurgical generator, a printed circuit board, a generator ground and a patient ground. The printed circuit board is disposed in mechanical cooperation with the electrosurgical generator and includes a plurality of conductive layers. The generator ground includes a first portion and a second portion. The first portion is electro-mechanically connected to a conductive layer of the printed circuit board and the second portion is electro-mechanically connected to another conductive layer of the printed circuit board. The patient ground includes a portion that is at least partially interposed between the first portion of the generator ground and the second portion of the generator ground.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 11/881,945, filed Jul. 30, 2007, the entirecontents of which is incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to electrically isolating a patient frommedical equipment, and more particularly, to electrically isolating apatient ground from a ground of an electrosurgical generator.

2. Background of Related Art

Patients undergoing medical procedures are generally electricallyisolated from stray electrical energy of medical equipment connected tothe patient. For non-interventional procedures (no medical devices areinserted into the subject), isolation of the patient from the medicaldevice is accomplished by incorporating insulating materials in theconstruction of surfaces that the patient is likely to touch (e.g.surface coils, patient bed, etc.).

For interventional procedures (medical devices are inserted into thesubject), the issue of patient isolation is more complicated sinceinterventional devices themselves are in contact with the patient. Thiscan be especially critical if the invasive device is in contact withelectrically-sensitive tissue (e.g., cardiac muscle, brain tissue,etc.). Due to the nature of microwave energy delivery for therapeuticprocedures, special requirements exist in isolating a patient, such asthe construction of an isolation circuit for use with a microwavegenerator.

The issue of isolating a patient ground from a generator's ground (i.e.,Earth ground) is complex in microwave generators having frequenciesabove about 500 MHz. In generators with lower frequencies, a transformermay be used to isolate the patient from the generator's ground. As thefrequencies get higher, the core loss of the transformer and parasiticelements often overwhelm attempts to transfer energy across an isolationboundary.

Another method of isolating a patient ground from a generator's groundmay be with the use of a capacitor. However, with microwave frequencies,the capacitors will add their own losses in terms of reflections andparasitic losses due in part to the voltage isolation requirements ofthe capacitor.

Accordingly, a need exists for improved devices and methods of isolatinga patient ground from a ground of an electrosurgical generator.

SUMMARY

The present disclosure relates to an electrosurgical system for treatingtissue. The system includes an electrosurgical generator, a printedcircuit board, a generator ground and a patient ground. The printedcircuit board is disposed in mechanical cooperation with theelectrosurgical generator and includes a plurality of conductive layers.The generator ground includes a first portion and a second portion. Thefirst portion is electro-mechanically connected to a conductive layer ofthe printed circuit board and the second portion is electro-mechanicallyconnected to another conductive layer of the printed circuit board. Thepatient ground includes a portion that is at least partially interposedbetween the first portion of the generator ground and the second portionof the generator ground.

The present disclosure also relates to a printed circuit board for usewith a microwave generator. The printed circuit board includes a firstconductive layer, a second conductive layer, a third conductive layer, afirst dielectric layer, a second dielectric layer and a microstrip. Thefirst conductive layer is configured for electro-mechanical engagementwith a first portion of a generator ground. The second conductive layeris configured for electro-mechanical engagement with a portion of apatient ground. The third conductive layer is configured forelectro-mechanical engagement with a second portion of the generatorground. The first dielectric layer is interposed at least partiallybetween the first conductive layer and the second conductive layer. Thesecond dielectric layer is interposed at least partially between thesecond conductive layer and the third conductive layer. The microstripis disposed in mechanical cooperation with a surface of the printedcircuit board.

DESCRIPTION OF THE DRAWINGS

Embodiments of the presently disclosed ground isolation systems aredisclosed herein with reference to the drawings, wherein:

FIG. 1 is a schematic view of an electrosurgical system in accordancewith an embodiment of the present disclosure;

FIG. 2 is a schematic perspective view of a printed circuit board foruse with the electrosurgical system of FIG. 1;

FIG. 3 is a cross-sectional view of a portion of the printed circuitboard of FIG. 2;

FIG. 4 is a schematic view of microstrip lines of the printed circuitboard of FIGS. 2 and 3; and

FIG. 5 is a schematic view of an electrical component of the printedcircuit board of FIGS. 2 and 3.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the presently disclosed electrosurgical systems andcomponents thereof are described in detail with reference to thedrawings, in which like reference numerals designate identical orcorresponding elements in each of the several views.

An electrosurgical system, including, for example, a microwave ablationsystem, for treating tissue in accordance with the present disclosure isreferred to in the figures as reference numeral 100. Referring initiallyto FIG. 1, electrosurgical system 100 includes an electrosurgicalgenerator 110 having a printed circuit board 120 disposed inelectro-mechanical cooperation therewith. Electrosurgical system 100 mayalso include a surgical instrument 200 (e.g., a microwave ablationdevice).

With reference to FIGS. 2 and 3, printed circuit board 120 includes aplurality of layers 130. Layers 130 are shown having enlargedthicknesses for clarity. Specifically, layers 130 of printed circuitboard 120 include at least a first conductive layer 130 a, a firstdielectric layer 130 b, a second conductive layer 130 c, a seconddielectric layer 130 d, a third conductive layer 130 e and a thirddielectric layer 130 f as illustrated. In particular, as seen in FIG. 2,first dielectric layer 130 b is shown interposed between firstconductive layer 130 a and second conductive layer 130 c of printedcircuit board 120. Second dielectric layer 130 d is shown interposedbetween second conductive layer 130 c and third conductive layer 130 eof printed circuit board 120. Third dielectric layer 130 f is shownadjacent third conductive layer 130 e.

Electrosurgical generator 110 includes a generator ground 140electrically connected to printed circuit board 120. Generator ground140 includes at least a first portion 142 and a second portion 144.First portion 142 of generator ground 140 may be electro-mechanicallyconnected to a conductive layer (e.g., first conductive layer 130 a) ofprinted circuit board 120. Second portion 144 of generator ground 140may be electro-mechanically connected to a different conductive layer(e.g., second or third conductive layer 130 c or 130 e) as compared tofirst portion 142.

Electrosurgical generator 110 further includes a patient ground 150 thatis electro-mechanically connected to a conductive layer (e.g., secondconductive layer 130 c). Patient ground 150 may be at least partiallyinterposed between first portion 142 of generator ground 140 and secondportion 144 of generator ground 140.

As can be appreciated, both generator ground 140 and patient ground 150are configured to allow an electrical current to flow therethrough. Thecurrents include a frequency having a particular wavelength. Asillustrated in FIG. 3, it is envisioned that at least two adjacentconductive layers (e.g., first conductive layer 130 a and secondconductive layer 130 c) of printed circuit board 120 overlap one anotherby at least a distance “d₁” equaling about ¼ of one wavelength of theelectrical current flowing from generator ground 140 and/or patentground 150. In one particular embodiment, distance “d₁” may be about 4.0inches (10.16 cm). The overlapping of adjacent conductive layers (e.g.,conductive layers 130 a, 130 c) helps minimize various losses incurredby generator ground 140 and/or patient ground 150, particularly withrespect to their use in microwave generators with frequencies of morethan about 500 MHz.

According to various embodiments of the present disclosure, illustratedin FIG. 2 and schematically in FIG. 4, printed circuit board 120 mayinclude a microstrip 160 disposed in mechanical cooperation with asurface thereof. Microstrip 160 facilitates a user's ability to tuneprinted circuit board 120 to help optimally reduce losses incurred bygenerator ground 140 and/or patient ground 150. For example, lengthsand/or widths of an active line 166 (e.g., disposed inelectro-mechanical cooperation with microwave ablation device 200 andconfigured to transmit energy to microwave ablation device 200) and/ormicrostrip 160 can be varied to help tune printed circuit board 120. Itis envisioned that microstrip 160 is between about 0.0787 inches (2.00mm) and about 0.0827 inches (2.10 mm) wide and, in an embodiment, may beabout 0.0807 inches (2.05 mm) wide. In an embodiment, where microstrip160 is about 0.0807 inches (2.05 mm) wide, the impedance may equal about27.3 ohms and its length may be about 2.5 inches (63.5 mm). Microstrip160 may have a thickness equal to about the thickness of copper (about70 μm or 2.7 mils) plus the thickness of any dielectric associatedtherewith (about 0.5 mm to about 1.5 mm or about 20 mils to about 60mils. Microstrip 160 may be constructed of a suitable electricallyconductive material, such as, for example copper, silver, and/or gold.

Microstrip 160 may be schematically illustrated in FIG. 4 to include atleast one inductor 162 and at least one capacitor 164, such that thecharacteristic impedance (I) of the transmission line may be representedby:

$I = \sqrt{\frac{inductor}{capacitor}}$

As seen in FIG. 4, microstrip 160 is shown including three inductors 162a, 162 b, 162 c connected in series, two capacitors 164 a, 164 bconnected in parallel between inductors 162 a, 162 b, 162 c, an activeline 166 and a ground line 168. It is envisioned that capacitors 164 aand 164 b are separated by a distance “d₂”, which may be about 2.3622inches (60 mm).

With reference to FIG. 5, ground line 168 a represents the couplingbetween generator grounds 140 and patient ground 150, where capacitor164 c represents the sum of capacitance coupling between first portion142 of generator ground 140 and patient ground 150, and between secondportion 144 of generator ground 140 and patient ground 150.

As illustrated, printed circuit board 120 may include a plurality ofvias 170 disposed at least partially therethrough (FIGS. 2 and 3).Specifically, printed circuit board 120 of FIG. 2 is shown having vias170 disposed at various locations around printed circuit board 120 andin a predetermined arrangement. FIG. 3 illustrates a cross-section of aportion of printed circuit board 120 taken through a singe via 170. Itis envisioned that vias 170 electrically connect first portion 142 ofgenerator ground 140 with second portion 144 of generator ground 140. Ina disclosed embodiment, a plurality of vias 170 are spaced less thanapproximately 15° of a wavelength from adjacent vias 170; for example afirst via 170 a is spaced less than approximately 15° of a wavelengthfrom an adjacent second via 170 b (See FIG. 2). A via pattern 170 c isconfigured such that vias 170 at least partially surround patient ground150, thus helping to increase the coupling between generator ground 140and patient ground 150. Additionally, the spacing of via pattern 170 cfrom patient ground 150 may be electrically separated to ensure arelatively high dielectric standoff between patient ground 150 andgenerator ground 140 at relatively low frequencies (approximately 60 Hz,for instance). Further, the spacing of vias 170 is configured toencompass patient ground 150 in an electrical box. That is, a topportion and a bottom portion of patient ground 150 are each coupled tofirst portion 142 and second portion 144 of generator ground 140 and aside portion of patient ground 150 is coupled to plurality of vias 170.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplifications of variousembodiments. Those skilled in the art will envision other modificationswithin the scope and spirit of the claims appended hereto.

1. A printed circuit board for use with a microwave generator, theprinted circuit board comprising: a first conductive layer configuredfor electro-mechanical engagement with a first portion of a generatorground; a second conductive layer configured for electro-mechanicalengagement with a patient ground; a third conductive layer configuredfor electro-mechanical engagement with a second portion of the generatorground; a first dielectric layer interposed at least partially betweenthe first conductive layer and the second conductive layer; a seconddielectric layer interposed at least partially between the secondconductive layer and the third conductive layer; and a microstripdisposed in mechanical cooperation with a surface of the printed circuitboard.
 2. The printed circuit board of claim 1, wherein the generatorground includes a frequency having a wavelength and the patient groundincludes a frequency having a wavelength, and wherein at least twoadjacent conductive layers of the printed circuit board overlap oneanother by about ¼ of one wavelength of at least one of the generatorground and the patient ground.
 3. The printed circuit board of claim 1,further including a plurality of vias disposed at least partiallytherethrough.
 4. The printed circuit board of claim 3, wherein spacingbetween adjacent vias of the plurality of vias is less than about 15°.5. The printed circuit board of claim 1, further including an activeline configured to transmit energy to a microwave ablation device. 6.The printed circuit board of claim 1, wherein the second conductivelayer is at least partially interposed between the first conductivelayer and the third conductive layer.
 7. The printed circuit board ofclaim 1, wherein at least two adjacent conductive layers overlap oneanother by about four inches.
 8. The printed circuit board of claim 5,further including a first capacitor and a second capacitor disposed inmechanical cooperation with the active line, the first capacitor and thesecond capacitor configured to isolate the active line.
 9. The printedcircuit board of claim 1, wherein the microstrip includes at least oneinductor and at least one capacitor.
 10. A printed circuit board for usewith a microwave generator, the printed circuit board comprising: afirst conductive layer configured for electro-mechanical engagement witha first portion of a generator ground; a second conductive layerconfigured for electro-mechanical engagement with a patient ground; anda third conductive layer configured for electro-mechanical engagementwith a second portion of the generator ground, wherein the first andthird conductive layers are insulated from the second conductive layer.11. The printed circuit board of claim 10, wherein the generator groundincludes a frequency having a wavelength and the patient ground includesa frequency having a wavelength, and wherein at least two adjacentconductive layers of the printed circuit board overlap one another byabout ¼ of one wavelength of at least one of the generator ground andthe patient ground.
 12. The printed circuit board of claim 10, whereinthe second conductive layer is at least partially interposed between thefirst conductive layer and the third conductive layer.
 13. The printedcircuit board of claim 10, further including a plurality of viasdisposed at least partially therethrough interconnecting the first andthird conductive layers.
 14. The printed circuit board of claim 13,wherein spacing between adjacent vias of the plurality of vias is lessthan about 15°.
 15. The printed circuit board of claim 10, wherein atleast two adjacent conductive layers overlap one another by about fourinches.
 16. The printed circuit board of claim 10, further including anactive line configured to transmit energy to a microwave ablationdevice.
 17. The printed circuit board of claim 16, further including afirst capacitor and a second capacitor disposed in mechanicalcooperation with the active line, the first capacitor and the secondcapacitor configured to isolate the active line.
 18. The printed circuitboard of claim 10, further including at least one dielectric layerinterposed at least partially between at least two adjacent layers. 19.The printed circuit board of claim 18, wherein a first dielectric layeris interposed at least partially between the first conductive layer andthe second conductive layer.
 20. The printed circuit board of claim 18,wherein a second dielectric layer is interposed at least partiallybetween the second conductive layer and the third conductive layer.